Pavement



(No Model.)

W. LAKE.

PAVEMENT.

mZLa/ bm LAMA-F (lr/kk Nrrnn VSTATES PATENT Ottica.

WILMOT LAKE, OF CHARLTON HEIGHTS, MARYLAND.

PAVEM ENT.

SPECIFICATION forming part 0f Letters Patent N0. 507,683, dated October 31, 1893.

Application iiled September 29, 1892. Serial No. 447,264.- (No model.)

To a/ZZ whom t may concern:

Be it known that I, WILMOT LAKE, a citizen of the United States, residing at Charlton Heights, in the county of Prince Georges and l State of Maryland, have invented certain new and useful Improvements in Pavements and Methods of Laying the Same; and I do hereby declare the following.,r to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawing, and to the letters of reference marked thereon, which forms a part of this specification. l

The invention relates particularly to the class of concrete pavements made with a hydraulic cement base and an asphalt concrete surface, but though designed to remedy defects, incident to pavements of this class as now constructed, the invention is applicable to pavements of any characterthat are made with a base course that is at any stage plastic, and a superposed layer applied in a plastic or comminuted state. The weak point in pavements of the special character above referred to, is the insufticient bond between the binder and the cement base, or the asphalt top course and the base if no binder is used, in consequence of which the binder working loose from the base, develops ridges and depressions or waves in the surface that soon destroy the pavement, and the object of the present invention is to produce a pavement of such a construction that the bond between the binder and the base, or the asphalt surface and the base, if no binder is used, shall be as strong as that between any parts of the base itself. This being secured, there cannot be any movement or displacement of the surface or binder with respect to the base, but the whole pavement becomes a solid block of which the bond between the base and the superposed layer is as irm and strong as any other part thereof.

In the case of asphalt pavements laid with a bituminous base, it is found that the bituminous matrix of the base under the action of summer heat gradually works downward, to a greater or less extent. The matrix of the binder likewise seeks a lower level, and the asphalt ofthe surface in turn works downward into the binder or the base, bringing the stone of the binder to the surface. Further, if there is a soft spot in the ground beneath, or a depression, the pavement, base and all, will gradually settle at that point and a hollow will appear on the surface. In the case of a pavement laid with a cement or a hydraulic concrete base these elements of destruction do not exist, and the bituminous elements of the binder, or the top cannot work down into the base, but as before stated, the imperfect bond between the base and the overlying course is a serious defect. When the base is bituminous, the matrix of the binder and the base coalesce and form a strong bond, but in the case of a cement base there is no coalescing of the matrices of the two layers, that of the upper layer works into and fills any depressions there maybe in the surface of the cement base,but as the cement base is rammed and packed hard and then allowed to set before the binder course is added, and the latter is applied directly to the rammed and substantially smooth-surfaced base, the mechanical bond between the two layers is of little practical value. To overcome these defects, I produce a concrete pavement having a base and an overlying course with abond of clean broken stone between the two courses, each stone of the bond being partly bedded in the base course and partly in the overlying layer, binder or top as the case may be.

In layinga pavement according to the oresent invention, I first lay a base of hydraulic concrete, indicated by Ain the accompanying drawing; then, before this has set, but after it has been well ram med, I spread thereon a thin layer of clean broken stone, B, the stones being about two inches in size. This stone is spread so that stones will not lie on each other, but all rest on the concrete. The stone is then rammed sufliciently to bed them one half into the cement base and it is then left to set, with the clean faced bonding course of stones B projecting one half out from the ICO less the asphalt course is spread directlyon the bonding stones B and the binder, so called, omitted.

It will be seen from the manner of procedure, that the faces of the stones B presented respectively, to the cement course below, and the binder or top course above, are clean faces,free from bituminous mat-ter in one case, and from cement or dirt in the other, and hence the adhesion of the matrix of the respective courses to the binding stone is not impaired.

The described pavement having a hydraulie cement base, and an upper course or layer of concrete, and a bonding course of broken stones embedded into said cement base and course of concrete, with their upper ends covered by and standing some depth below the upper surface of the course of concrete, substantially as set forth.

In testimony whereof Iafflx mysignature in presence of two Witnesses.

VILLWIOT LAKE.

Witnesses: v

G. Y. ATLEE, STORY B. LADD. 

